The present invention relates to an apparatus and a method for automated assembly of electronic circuits.
Usually, for this purpose, program controlled placing devices are used which are capable of taking a circuit component from a stack and inserting it at a given position of a circuit board. When the placing process is finished, the circuit board is heated together with the components placed on it in order to melt solder and to bring the circuit components into contact with conductors of the circuit board.
The process steps of placing and heating are carried out by different devices which, for a completely automated operation, must comprise internal conveyor means which receive a circuit board to be processed at an input of the device, and convey it to a processing location where the circuit board is packed with the components or the components are soldered, respectively, and further to an output of the device. These internal conveying means are often formed with conveyor belts. At a transition from one device to another, these conveyor belts are generally butt jointed, so that a circuit board which is delivered by a conveyor belt of the placing device may slide across the joint onto the conveyor belt of the soldering device and may be further transported by it. Lateral guide rails ensure that the circuit board arrives on the conveyor belt of the soldering device exactly in a correct orientation.
Such a device set-up provides satisfactory results when circuits having working frequencies in the MHz range are assembled. For assembling radio frequency circuits with working frequencies in the GHz range, they have proved unsatisfactory. The reason for this is that, in radio frequency circuits, a much higher positional accuracy is required for the individual circuit components. There are placing devices available which are capable of placing the individual circuit components with the required accuracy onto a circuit board; however, after soldering it is often found that the circuit components are no longer at the intended locations with the required accuracy. An undesirable scatter in the technical properties of the circuit or even circuit failures may result.